Electrical-arc-flash hazards are a known threat in some workplaces and must be addressed to protect people who may be exposed to such dangerous conditions. Electric-arcs or flashes can result from short circuits developing from poor electrical grounding, failure of insulation, or workers inadvertently contacting exposed electrical circuit elements with objects such as tools. Electric-arcs have extremely high temperatures and near explosive power, and the energy they radiate can result in serious or fatal injury. To protect workers from exposure to such arc-flash events, a number of protective safety devices have been developed. In particular, face shields employing generally transparent windows comprised of compositions which have the ability for the user of the shield to see the workspace and, at the same time, have the ability to substantially block harmful radiation, are available. These devices are designed to provide protection against the thermal, optical, and mechanical hazards generated by arc-flash events. The protective compositions are referred to as energy absorbing materials and are classified by their calorie ratings, that is, the level of energy they have been tested or certified for.
The protective window of such a protective face shield is securely attached to the retainer structure of the shield and is structured to provide maximum protection to the user. In particular, the installation is designed to prevent radiation leaks around the periphery of the window.
Because of the need to protect a user from the electromagnetic energy of an arc-flash event, protective face shields have, of necessity, been relatively well sealed around the face of the user. Lack of adequate ventilation is a typical consequence of the face shield being sealed, and additions such as fans have been employed in some face shields to provide needed ventilation. Even then, moisture and fogging sometimes result because of inadequate provision for air to easily exhaust from near the front inside of the face shield. It has been difficult to ventilate arc shields because of the potential arc-flash energy that could enter the shield through vents or slots. Additionally, voice communication by the user is difficult and words or other sounds tend to be muffled from inside the face shield or maybe partially blocked from adjacent team members.
Generally related prior art devices are shown in FIGS. 1-3. These are provided for reference purposes, to show examples of protective face shields.